Machine for the production and cleaning of exposed aggregate slabs

ABSTRACT

Exposed aggregate slabs are produced in an automatic machine wherein two or more base plates, each having an elastic top portion, circulate along an endless path and are moved seriatim into register with a form which carries vibrators and is transported to and from a position of alignment with the ram of a vertical press. The form receives a layer of aggregate and a charge of cementing agent whereby the layer of aggregate rests on the elastic portion of a base plate. Upon completion of the compacting operation, the freshly produced slab is removed from the form with the respective base plate and is transferred onto one of a series of pallets on a stepwise operated conveyor. Such transfer takes place simultaneously with tilting of the slab from a horizontal into a vertical plane and with separation from the base plate. The front side of the slab is rinsed or cleaned while the slab rests on a pallet whereby the rinsing or cleaning action results in removal of traces of cementing agent from the outer side of the aggregate layer. The slabs on a fully loaded pallet are then transferred to a final curing station.

Boehringer et al.

1 MACHINE FOR THE PRODUCTION AND CLEANING OF EXPOSED AGGREGATE SLABS [75] Inventors: Paul Boehringer, Oedheim; Erwin Heiligenmann, Bad Rappenau, all of Germany [73]- Assignec: Boehringer & Co., Oedheim,

Germany [22] Filed: Dec. 15, 1972 [21] Appl. No.: 315,642

[30] Foreign Application Priority Data Dec. 17, 1971 Germany 2162850 [52] US. Cl. 425/253; 425/88; 425/257; 425/404; 425/413; 425/454; 425/455 [51] Int. Cl. B28B 15/00 [58] Field of Search 425/88, 110, 125-126,

[56] References Cited UNITED STATES PATENTS 315.414 4/1885 lttner 425/404 1,588,841 6/1926 Knapp 264/233 1,982,730 12/1934 Erkman 425/134 2,682,676 7/1954 Franchi 134/172 2,834,317 5/1958 Eger et a1 118/504 2,856,668 10/1958 Cravens 425/452 2,990,069 6/1961 Repasky et a1. 425/452 3,002,249 Jackson 425/134 Primary ExaminerRobe1t D. Baldwin Assistant ExaminerJohn McQuade Attorney, Agent, or Firm-Michael S. Striker [57] ABSTRACT Exposed aggregate slabs are produced in an automatic machine wherein two or more base plates, each having an elastic top portion, circulate along an endless path and are moved seriatim into register with a form which carries vibrators and is transported to and from a position of alignment with the ram of a vertical press. The form receives a layer of aggregate and a charge of cementing agent whereby the layer of aggregate rests on the elastic portion of a base plate. Upon completion of the compacting operation, the freshly produced slab is removed from the form with the respective base plate and is transferred onto one of a series of pallets on a stepwise operated conveyor. Such transfer takes place simultaneously with tilting of the slab from a horizontal into a vertical plane and with separation from the base plate. The front side of the slab is rinsed or cleaned while the slab rests on a pallet whereby the rinsing or cleaning action results in removal of traces of cementing agent from the outer side of the aggregate layer. The slabs on a fully loaded pallet are then transferred to a final curing station.

34 Claims, 19 Drawing Figures US. Patent Nov. 18,1975 Sheet10f16 3,920,369

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US. Patent Nov. 18,1975 Sheet7of 16 3,920,369

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U.S. Patent Nov.'18, 1975 Sheet90f 16 3,920,369

US. Patent Nov. 18,1975 Sheet 10 of 16 3,920,369

U.S. Patent Nov. 18, 1975 Sheet110f16 3,920,369

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US. Patent Nov. 18, 1975 U.S..Patent Nov. 18, 1975 Sheet 14 of 16 3,920,369

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Flg 18 O 4 F|g.17 XVIII MACHINE FOR THE PRODUCTION AND CLEANING OF EXPOSED AGGREGATE SLABS BACKGROUND OF THE INVENTION The present invention relates to improvements in machines for the production of so-called exposed aggregate plates or slabs wherein one side of the product is formed by a layer or stratum of aggregate which has been exposed as a result of washing to remove a coating of partially cured concrete. More particularly, the invention relates to an automatic machine for the massproduction of exposed aggregate slabs havin'g front sides formed by layers of coarse and/or fine aggregate, such as particles of crushed granite, hard rock, marble and/or others.

Exposed aggregate slabs are normally produced by resorting to a form and a base plate onto which the aggregate is placed prior to introduction of concrete, mortar or other suitable cementing agent (hereinafter called cement) on top of the aggregate layer to fill the form and to provide a backing which is caused to harden and to thereby hold the particles of aggregate in position. In accordance with a presently known procedure, base plates are stored in a magazine and are removed therefrom one after the other to advance along a predetermined path extending through a production line where the base plates are separably assembled with a form which thereupon receives a layer of aggregate and a mass of cement to produce a green or uncured slab. The base plate with the uncured slab thereon and with the form around theuncured slab is thereupon introduced into a ramming'or compacting unit where the contents of the form are condensed prior to transfer of the base plate, with the condensed slab thereon, into a curing station. The withdrawal of base plates from the magazine and the transport of base plates with condensed slabs thereon is carried out by hand so that the procedure is slow and the output is very low. Also, the cost of such slabs is very high because each base plate and each slab must be handled by several workmen. As a rule, the transport to final curing station is preceded by transport to a preliminary curing station where the cement is allowed to harden to an extent which should suffice to permit safe handling during washing at a washing station. The washing station is normally provided with means fordirecting against one side of a partially cured slab one or more jets of water to wash away 2 nary curing takes up much time so that the making of fresh slabs must be terminated well ahead of the end of a shift unless the workmen are allowed to work overtime with attendant increased expenditures for manhours.

Additional problems arise in connection with removal of the coating of cement at the front side of a partially cured slab. Thus, and in order to insure the removal of all particles of cement, it is considered necessary to'remove relatively large quantities of such material. This results in substantial losses in cementing agent and high expenditures in energy for compression and conveying of washing liquid. The interval of time which is spent for washing cannot be reduced at will because, if the water pressure is increased beyond a certain limit, the jets of water are likely to wash away or to comminute the particles of the aggregate layer. The resulting cracks in the aggregate layer allow water to penetrate into and behind the layer of aggregate in a finished slab so that the quality of the front surface is likely to be affected on freezing.

SUMMARY OF THE INVENTION An object of the invention is to provide an automatic machine for the mass-production of exposed aggregate slabs which can be controlled and attended to by a minimal number of workmen, whichcan turn out large gate.

the coating of cementat the front side, i.e., at that side where the aggregate layer is to be exposed to impart to the slab its eye-pleasing appearance. It is customary to delay the curing-of the cost of cement at the frontside of a freshly produced slab so as to insure that the main portion of the slab (namely, the body of cement behind the aggregate layer) will harden sufficiently to allow for safe manipulation of slabs without cracking, breakage and/or chipping but that .the coating at the front side will remain soft enough so as to enable the water sprays to remove such coating within a relatively short period of time. It was found that, in spite of such precautionary measures, the slabs are likely to break, chip and/or crack so that manythereof must be discarded or re-v duced in size. Also, a relatively heavy slab whose main body of cement is only partially cured is likely to warp during transport toward. during treatment at, and during removal from the washing station. Moreover, the just described conventional machine cannot operate at full capacity during an entire shift because the prelimi- Another object of the invention is to provide a machine wherein all operations, particularly those requiring the exertion of a substantial effort, are carried out automatically and in a predeterminedsequence so that the output of the machine greatly exceeds the output of presently known slab making machines.

A further object of the invention is to provide a machine wherein the coating of cement at the front side of a partially cured slab can be removed within a short interval of time and by one or more readily available instrumentalities including mechanical coat removers.

An additional object of the invention is to provide a machine which can produce slabs of any desiredsize and/or shape, which can produce relatively large slabs alternately with smaller slabs, and which can be rapidly converted for the manufacture of slabs having a desired finish at the front side and/or a desired size or shape.

Still another object of the invention is to provide a machine which is capable of mass-producing exposed aggregateslabsin such a way that the quantity'of cementing agent at the front side of the slab is reduced to a minimum so that the relatively small quantities of cement atthe front side can be removed in a time-saving operation and by exertion of forces which cannot dislodge or comminute the particles of the aggregate layer.

A further object of the invention is to provide the machine with novel and improved slab compacting or ramming means and with novel and improved means for transporting base plates and slabs past a plurality of slab forming and treating stations.

An additional object of the invention is to provide a machine which occupies a small amount of floor space and wherein a large number of finished but not completely cured slabs can be stored in a small area.

The invention is embodied in a machine for making exposed aggregate slabs of the type wherein at least the front side of the slab is formed by a layer of aggregate particles which are held together by a hardenable cementing agent. The machine comprises at least one form for reception of charges including particles of aggregate and cementing agent, at least one base plate which is movable into register with and then constitutes the bottom wall of the form and which includes a top layer or portion consisting of elastomeric material, means for feeding charges of cementing agent into the form and aggregate particles onto the base plate so that the particles form a layer resting on the top portion of the base plate, compacting means including a press and agitating means and being actuatable to compact the charge in the form so that the charge is converted into a slab resting on the base plate, a supply of pallets, transfer means which is actuatable to transfer slabs from the base plate onto the pallets, and a cleaning unit (preferably a washing and/or rinsing unit) which is arranged to clean the front sides of successive slabs on the pallets.

The machine preferably employs a series of base plates and a transporting device which can move the base plates along an endless path to place successive base plates into register with the form prior to introduction of cementing agent into the form. The particles of aggregate may be fed onto the base plates prior or subsequent to movement of base plates into register with the form.

The pallets are preferably movable by a conveyor which can advance the pallets in stepwise fashion to provide room for successively produced slabs. Each pallet may support one, two or more slabs and each slab is preferably tilted to move from a horizontal plane into a vertical plane during transfer from the slab forming station onto a pallet.

The cleaning unit is preferably mounted at a level above that pallet which is ready to receive a freshly produced slab, and the machine preferably further comprises an attaching device for suitable carriers or shoes which are applied to one edge face of each slab before the slab is placed onto a pallet so that the thus applied carrier rests on the pallet and supports the respective slab.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved slab making machine itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic plan view of a slab making machine which embodies one form of the invention;

FIG. 2 is a vertical sectional view as seen in the direction of arrows from the line IIII of FIG. 1;

FIG. 3 is a schematic plan view of a second slab making machine;

FIG. 4 is a diagrammatic plan view ofa third machine which constitutes a modification of the machine shown in FIG. 3, with the parts located above the path for base plates omitted for the sake of clarity (see the line IV-IV of FIG. 5);

FIG. 5 is a side elevational view of a portion of the machine shown in FIG. 4;

FIG. 6 illustrates the structure of FIG. 5 but with the form in a different position;

FIG. 7 is a transverse vertical sectional view as seen in the direction of arrows from the line VIIVII of FIG. 5;

FIG. 8 is a transverse vertical sectional view as seen in the direction of arrows from the line VIIIVIII of FIG. 5;

FIG. 9 is a sectional view similar to that of FIG. 8 but showing a portion of a modified machine;

FIG. 10 is an enlarged elevational view as seen in the direction of arrow X shown in FIG. 4;

FIG. 11 shows the structure of FIG. 10 but with the parts of a carrier attaching unit in different positions;

FIG. 12 is an elevational view as seen in the direction of arrow XII shown in FIG. 4;

FIG. 13 illustrates a detail as seen in the direction of arrow XIII shown in FIG. 11;

FIG. 14 is an enlarged view of a detail as seen in the direction of arrow XIV shown in FIG. 3;

FIG. 15 is a plan view of the structure shown in FIG. 14;

FIG. 16 is a view as seen in the direction of arrow XVI shown in FIG. 14;

FIG. 17 is a plan view of a pallet;

FIG. 18 is a side elevational view of the pallet as seen in the direction of arrow XVIII shown in FIG. I7; and

FIG. 19 is an end elevational view of the pallet as seen in the direction of arrow XIX shown in FIG. 18.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 1 and 2, there is shown a slab making machine which comprises a slab forming station 1 and utilizes a form or mold 4 which is movable in a horizontal plane between a first position 2 at the slab forming station 1 and a second position 3 at a ramming or compacting station. The removal of freshly formed exposed aggregate slabs 19 takes place at the station 1. The form 4 is of rectangular shape and has an open top defining a material-admitting opening 5 which can further receive successive base plates 6. The base plates 6 are moved into register with and deposited in the form 4 at the station 1 by a transporting device 7. Each base plate 6 comprises a bottom layer or portion 6a consisting of a hard metallic material (such as manganese steel) and a top layer or portion 8 consisting of rubber or an elastomeric synthetic plastic material. The portion 8 can be glued or vulcanized to the bottom portion 6a.

When the form 4 dwells in the position 2 at the slab forming station I, it receives a base plate 6 from the transporting device 7 in a first step. and thereupon receives a metered quantity of coarse and/or fin aggregate 11 which is to form a layer at the front side 44 of the finished slab 19. The aggregate 11 is supplied by way of a shute 9 and an aggregate feeding device or feeder 10 so that the metered quantity of aggregate ll descends onto the elastic top portion 8 of the base plate 6 which registers withthe form 4 at the station I. The form 4 is provided with vibrators or analogous agitating devices 12 which are actuated on admission of aggregate 11 so that the latter is distributed on the top portion 8 to form an even layer as shown in the right-hand portion of FIG. 2. The machine further comprises a second feeding device or feeder 13 which delivers into the form 4 (in the position 2 at the station 1) a'metered quantity of cement 14 before the thus filled form 4 (with the base plate 6 in register therewith) is transferred to the compacting station (position 3) where its contents are compacted by a ramming unit 16 including a press and the aforementioned agitating devices or vibrators 12 on the form 4. The press 15 comprises a vertically movable tamper or ram 17 which carries one, two or more additional agitating devices or vibrators 18. The conversion of metered quantities of aggregate 11 and cement 14 into a slab 19 takes place in response to vibration and subsequent compression at an elevated pressure.

In the next step, the form 4 is returned to the position 2 at the slab forming station 1 to be separated from the base plate 6 and from the freshly formed slab 19 thereon. The station 1 is located at a level above an ejector 20 which comprises spaced-apart upwardly extending knockout elements or fingers 21. When the fingers 21 are caused to move upwardly, eg. by a hydraulic jack, they lift the base plate 6 and the slab 19 above and away from the form 4. The base plate 6 (with the slab 19 thereon) is then accepted by a reciprocable portion of a transfer device 23 including a table 22 which can be pivoted or tilted through 90degrees. The fingers 21 are retracted downwardly and away from the base plate 6 as soon as the latter is supported by the reciprocable portion of the tiltable table 22. The table 22 is then moved in a direction to the left, as viewed in FIG. 2, so as to locate the base plate 6 and the slab 19 thereon above a conveyor 24 for pallets 43.

The evacuated form 4 at the station 1 is immediately assembled with a fresh base plate 6 which is lifted off the table 22 by a lifting mechanism 25 of the transporting device 7. The transporting device 7 is movable along an overhead guide rail 27 which is located above the ejector 20 and transfer device 22. The means for moving the device 7 along the guide rail 27 may comprise one or more driven endless chains, not shown. The transporting device 7 inserts the base plate 6' from above so that the composite mold including the form 4 (with the agitating devices 12 thereon) and the base 6 is ready to receive a fresh charge of aggregate 11 and cement 14.

The mechanism 25 which lifts the base plate 6 off the table 22 of the transfer device 23 comprises grippers 28 which can engage the marginal portions of the base plate 6 and are pivotably mounted on a holder 29. The grippers 28 form two rows spaced apart from each other by a distance which approximates the width of a base plate 6 or 6'. The holder 29 is movable up and down by a suitable motor, e.g., a hydraulic or pneumatic cylinder and piston unit 30. It is to be noted that the base plate 6' was used for the making of the preceding slab 19 and that is was left on the table 22 upon detachment of the preceding slab l9 therefrom. The lifting of the base plate 6 off the table 22' precedes the transfer of the next base plate 6 from the fingers 21 of the ejector 20. When the transporting device 7 (with the base plate 6' held by the grippers 28) is moved above and into register with the form 4 at the station 1, the cylinder 30 moves the holder 29 downwardly and the grippers 28 are disengaged from the base plate 6' by pivoting relative to the holder 29. The means for thereupon depressing the thus released base plate 6 into the form 4 at the station 1 comprises an inserting device 32 having two hydraulic or pneumatic cylinders 31 which are mounted on the holder 29 and whose pis- 6 ton rods are movable downwardly as soon as the grippers 28 are disengaged from the base plate 6'.

The slab 19 which rests on the base plate 6 is thereupon attached to a strip-shaped shoe or carrier 83 (see FIG. 11) by means of an attaching unit 34. The carrier 83 is placed adjacent to that (rear) side of the slab 19 which faces away from the base plate 6 and this carrier is secured to the slab 19 by a clamping device 35. The attaching unit 34 comprises two levers 33.

The table 22 is pivotable or tiltable through degrees by a turning or pivoting device 36 which includes two gear segments 37 mating with pinions 38 secured to a shaft 39 of the table 22. The latter is movable along a frame 40 in parallelism with the path of pallets 43 on and above the conveyor 24. During such movement along the frame 40, the shaft 39 of the table 22 is rotated by two or more rack and pinion drives 41, 42 whereby the gear segments 37 cause the table 22 to pivot with the slab 19 until the carrier 83 comes to rest on a pallet 43 which is being supported by the conveyor 24. The front side 44 of the slab 19 on the respective pallet 43 is then located in a substantially vertical plane and faces the transfer device 23 including the table 22.

The washing or rinsing unit 46 for the front side 44 of the freshly produced slab 19 is connected with one lever 33 of the attaching unit 34 by a linkage 45 which can move the washing unit lengthwise of the conveyor 24. The washing or rinsing unit 46 is preferably also movable up and down or sideways in parallelism with the adjacent slab 19. The clamping device 35 is then disengaged from the slab 19 on the pallet 43. At the same time; the machine energizes several strong electromagnets 49 on the table 22 so that the electromagnets attract the base plate 6 and the latter is disengaged from the freshly produced slab 19 on the pallet 43 in response to renewed pivoting of the table 22 back to its original horizontal position. The base plate 6 is thereupon accepted by the transporting device 7 in the aforedescribed manner, i.e., it is engaged by the grippers 28 on the holder 29 of the lifting mechanism 25 and is ready to be returned into the form 4 at the slab forming station 1.

Prior to start of the washing or rinsing operation, the conveyor 24 advances thepallets 43 thereon by a step so as to provide room for a fresh slab 19 which is to be delivered with the base plate 6.

The conveyor 24 is a roller conveyor having two rows of rollers 50 in the form of pulleys driven by a pair of endless V-belts 51. The means for intermittently driving the rollers 50 by way of the respective belts 51 is not shown in the drawing. The undersides of the pallets 43 are provided with pairs of elongated legs 52 which rest on the upper stretches of the respective belts 51 to thus reduce the likelihood of shaking of slabs 19 during transport by the conveyor 24. The pallets 43 are stored in a magazine 53 which has suitable feeding means (not shown) for supplying a succession of pallets onto the right-hand end portion of the conveyor 24, as viewed in FIG. 1.

The levers 33 of the attaching device 34 withdraw strip-shaped carriers 83 for the slabs 19 from a magazine 54 which is located at a level above the conveyor 24 adjacent to the washing or rinsing unit 46. The details of the carriers 83 will be described with reference to FIGS. 10 and 11.

The washing or rinsing unit 46 comprises a horizontal tubular manifold 47 which supplies pressurized water or a mixture of water and air to a series of discrete 

1. In a machine for making exposed aggregate slabs of the type wherein at least the front side of each slab is formed by a layer of aggregate particles held together by a hardenable cementing agent, a combination comprising a form for reception of charges including particles of aggregate and cementing agent; a plurality of base plates, each including a top portion of elastomeric material; transporting means for moving said base plates along an endless path comprising a plurality of sections including a slab forming section where successive base plates register with and constitute the bottom wall of said form, and at least one second section; a conveyance for moving said form along said slab forming section and said transporting means including a drive which receives motion from said conveyance and which is arranged to move said base plates along said slab forming section and said second section of said path; means for feeding charges of cementing agent into said form and particles of aggregate onto that base plate which registers with said form so that the particles form a layer resting on the top portion of said registering base plate; compacting means including a press and agitating means actuatable to compact the charge in said form so that the charge is converted into a slab resting on said registering base plate; a supply of pallets; transfer means actuatable to transfer slabs from said base plates onto said pallets; and a cleaning unit arranged to clean the front sides of successive slabs on said pallets.
 2. A combination as defined in claim 1, wherein said drive includes at least one flexible element having ends secured to said conveyance and a stretch extending along said slab forming section, said stretch being provided with entraining means for moving successive base plates in a predetermined direction in response to movement of said conveyance in one of two opposite directions.
 3. A combination as defined in claim 1, wherein said drive comprises beams provided on said conveyance and entraining elements provided on said beams and arranged to move base plates along said slab forming section in response to movement of said conveyance in one of two opposite directions.
 4. In a machine for making exposed aggregate slabs of the type wherein at least the front side of each slab is formed by a layer of aggregate particles held together by a hardenable cementing agent, a combination comprising a form for reception of charges including particles of aggregate and cementing agent; a plurality of base plates, respectively movable into registry with and then constituting the bottom wall of said form, each of said base plates including a top portion of elastomeric material; means for forming a slab on each base plate while the same registers with said form; a supply of pallets; transfer means actuatable to transfer slabs from said base plates onto said pallets in upright position so that one of several edge faces of a thus deposited slab rests on the respective pallet; a cleaning unit arranged to clean the front sides of successive slabs on said pallets and comprising means for directing against said front sides of successive slabs sprays of pressurized fluid; and shielding means for shielding the remaining sides of such slabs from said fluid and comprising a pair of gripper arms having strips moveable into engagement with two of the other edge faces of a slab whose front side is cleaned by pressurized fluid.
 5. A combination as defined in claim 4, wherein said arms are pivotable about vertical axes and said shielding means further comprises means for pivoting said arms so as to move said strips into and from engagement with the respective edge faces of a slab therebetween.
 6. A combination as defined in claim 4, wherein each of said gripper arms further comprises a plate-like shield arranged to overlie portions of slabs adjacent to that slab whose front side is cleaned by pressurized fluid.
 7. In a machine for making exposed aggregate slabs of the type wherein at least the front side of each slab is formed by a layer of aggregate particles which are held together by a hardenable cementing agent, a combination comprising, a form for reception of charges including particles of aggregate and cementing agent; a series of base plates respectively movable into register with and then constituting the bottom wall of the form, each of said base plates including a top portion consisting of elastomeric material; means for feeding charges of cementing agent into said form and particles of aggregate onto the base plates so that the particles form a layer resting on said top portion, said feeding means comprising discrete first and second feeders for aggregate particles and cementing agent, said first feeder comprising a frame, a gate, movable into register with said frame to constitute the bottom wall thereof, means for moving said gate, and a conveyance for delivering metered quantities of aggregate particles into said frame and onto said gate, said base plates being movable seriatim in alignment with and below said frame and said gate to receive metered quantities of aggregate parTicles in response to movement of said gate from register with said frame whereby said particles descend onto said top portions of elastomeric material of the respective base plates; compacting means including a press and agitating means actuatable to compact the charge in said form so that the charge is converted into a slab resting on the respective base plate; a supply of pallets; transfer means actuatable to transfer slabs from said base plates onto said pallets; and a cleaning unit arranged to clean the front sides of successive slabs on said pallets.
 8. A combination as defined in claim 7, wherein said agitating means comprises at least one vibrator mounted on said form.
 9. A combination as defined in claim 7, wherein said press includes a ram movable into and from compressing engagement with charges in said form, said agitating means comprising at least one vibrator mounted on said ram.
 10. A combination as defined in claim 7, wherein said second feeder is actuatable to introduce into said form metered quantities of cementing agent subsequent to actuation of said first feeder so that the cementing agent is deposited onto a layer of aggregate particles on said top portion of said base plate.
 11. A combination as defined in claim 7, wherein said form is movable with the respective base plate between a first position of registry with at least one of said feeders and a second position of registry with said press.
 12. A combination as defined in claim 11, wherein said form is located in a horizontal plane during movement between and in said first and second positions thereof.
 13. A combination as defined in claim 11, wherein said one feeder is said first feeder and said form registers with said second feeder in said second position thereof.
 14. A combination as defined in claim 11, further comprising a conveyance arranged to move said form between said first and second positions.
 15. A combination as defined in claim 7, and transporting means for moving said base plates along an endless path including a portion where successive blase plates register with and constitute the bottom walls of said form.
 16. A combination as defined in claim 15, wherein said endless path comprises a plurality of sections including a slab forming section wherein successive base plates are moved into register with said form to support charges of aggregate particles and cementing agent prior to, during and subsequent to actuation of said compacting means.
 17. A combination as defined in claim 15, wherein said endless path comprises a plurality of sections including a slab forming section, a second section extending in parallelism with said slab forming section, and two additional sections along one of which the base plates advance from said slab forming section to said second section and along the other of which the base plates advance from said second section to said slab forming section.
 18. A combination as defined in claim 17, wherein said transporting means comprises drive means operable to move said base plates along said sections of said path.
 19. A combination as defined in claim 18, wherein said drive means includes discrete first and second drives for moving base plates along said additional sections.
 20. A combination as defined in claim 19, wherein said first and second drives are independently operable chain drives.
 21. A combination as defined in claim 7, wherein the cross-sectional area of said form exceeds the cross-sectional area of said frame.
 22. A combination as defined in claim 7, further comprising means for lifting successive base plates into register with said frame.
 23. A combination as defined in claim 7, further comprising means for moving said form between a position of alignment with said compacting means and a further position and including a second conveyance supporting said form, and means for lifting successive base plates into register with said frame, said means for lifting Being connected to and being movable with said second conveyance.
 24. A combination as defined in claim 7, wherein said cleaning unit is movable in a horizontal plane.
 25. A combination as defined in claim 7, wherein said cleaning unit comprises means for directing against the front sides of successively produced slabs sprays of a pressurized fluid and further comprising means for shielding the remaining sides of such slabs from said fluid.
 26. A combination as defined in claim 7, wherein said transfer means is arranged to deposit slabs on said pallets in upright position so that one of several edge faces of a thus deposited slab rests on the respective pallet, said shielding means including means for covering the other edge faces of the slab whose front side is cleaned by pressurized fluid.
 27. A combination as defined in claim 25, wherein said shielding means comprises a cover movable to and from a predetermined position in which it overlies the slab whose front side is cleaned by pressurized fluid.
 28. A combination as defined in claim 27, wherein said cover has a front portion which is flush with the front side of the slab which is being cleaned by pressurized fluid in said predetermined position of said cover.
 29. A combination as defined in claim 28, wherein said front portion of said cover includes a shroud extending vertically upwardly from the front side of the slab whose front side is being cleaned by pressurized fluid in said predetermined position of said cover.
 30. A combination as defined in claim 27, wherein said cover is pivotable about a horizontal axis and said shielding means further comprises means for pivoting said cover about said axis.
 31. A combination as defined in claim 26, wherein said means for covering includes sealing strips consisting of elasomeric material.
 32. A combination as defined in claim 25, further comprising a first frame supporting said shielding means and a second frame supporting said cleaning unit, one of said frames being movable relative to the other of said frames.
 33. A combination as defined in claim 7, wherein each of said pallets has a polygonal outline and includes a plurality of corner portions provided with plates having openings to facilitate stacking of loaded pallets.
 34. A combination as defined in claim 7, wherein said cleaning unit comprises a rotary brush. 